The present invention generally relates to a torsion angle detection apparatus and a torque sensor.
Generally a strain sensor is generally known which has a strain gauge pasted on a torsion bar, so that the torque values are adapted to be calculated from the changes in the resistance values to be caused by the strain of the torsion bar.
Also, a torque sensor of a magnetic phase difference system is also proposed where a pair of external gears are secured onto both the side portions of a torsion bar, internal gears are disposed in proximity to the external peripheries thereof, and a magnetic circuit is formed between them, so that the phase differences of the tooth of both the gears are adapted to be detected with the detection coils, and the torque values are adapted to be calculated from the phase differences thereof.
In the above described strain gauge system, minimum resolution is as rough as approximately 0.5 kgm, error is approximately 1%, response property is as low as approximately 2.5 kHz when the maximum measuring value is made 5 kgm by the use of a certain torsion bar, with a problem that a torque sensor of high accuracy and high speed response property cannot be made.
Although the minimum resolution is improved as far as 0.1 kgm, the error is improved as far as 0.1%, the response property is also improved as far as approximately 20 kHz when the maximum measuring value is 5 kgm likewise in the torque sensor of a magnetic phase difference system, a torque sensor of higher accuracy and higher speed response property cannot be provided. Also, as the output density of the detection signal per rotation is restricted in the tooth number of the gears, the torque changes cannot be detected precisely, and further the stable detection signal cannot be obtained in the case of the low speed rotation, so that a driving means for the internal gears is required to cope with them, with a problem that the construction becomes complicated.
Also, a similar problem is provided even in a torsion angle detection apparatus for the measured shaft of the same construction.